Computer-Aided Design (CAD) relates to software for constructing and manipulating complex three-dimensional (3D) models. A number of CAD systems and programs are offered in the marketplace that construct 3D models and enable engineers to design parts and assemblies, such as the product provided by Dassault Systèmes SolidWorks Corporation under the trademark SOLIDWORKS.
A number of different modeling techniques can be used to create a 3D model. One such technique is a solid modeling technique, which provides for topological 3D models where the 3D model is a collection of interconnected topological entities (e.g., vertices, edges, and faces). The topological entities have corresponding supporting geometrical entities (e.g., points, trimmed curves, and trimmed surfaces). The trimmed surfaces correspond to the topological faces bounded by the edges. CAD systems may combine solid modeling and other modeling techniques, such as parametric modeling techniques. Parametric modeling techniques can be used to define various parameters for different features and components of a model, and to define relationships between those features and components based on relationships between the various parameters. The parametric nature of a CAD system enables constraints (e.g., relationships between features) to influence the geometric representation of a model.
A CAD system manages models of objects, which are stored in one or more electronic files. The CAD system includes graphic tools for representing the modeled objects to design engineers; these tools may be dedicated to the display of both simple and complex objects. The graphical user interface (GUI) of the CAD system plays an important role in efficiently designing and manipulating a model.
A model of a part consists of features, which refer to the building blocks of the part. A feature may begin as a 2D sketch and then be extruded to become a boss or a hole, for example. A sketch, as is familiar to those skilled in the art, is a collection of lines and other 2D or 3D objects on a plane or face that forms the basis for a feature such as a base or a boss. A 3D sketch is a non-planar object and can be used to guide a sweep or loft, for example.
Not all features are based on a sketch; other features may be applied to a part. For example, a fillet feature when applied to a part rounds one or more edges, a chamfer feature creates a beveled edge, and a draft feature adds an angle to one or more faces in a part.
Constructing a model in a CAD system may entail creating a feature from a 2D or 3D sketch. The sketch consists of geometry, such as points, lines, and curves. Dimensions are added to the sketch to define the size and location of the geometry.
In addition to allowing a design engineer to create a sketch by drawing lines to create a shape, a CAD system provides sketch templates from which a design engineer initiates or builds a sketch. Each sketch template specifies a respective primitive shape or element (e.g., a circle or a rectangle).
A drawback of a number of CAD systems is the lack of a wider variety of geometric primitives. For example, a CAD system may provide line, circle, and rectangle primitives, but not a customized profile. Another drawback, affecting how efficiently a model can be created, is that primitives, including blocks that allow the grouping of sketch entities, although re-usable, have pre-determined sizes and cannot be manipulated or modified.
Macros are used to automate redundant and simple tasks. As used in the SolidWorks® application, macros are a means in which shapes can be defined by recording keyboard commands, for example. In general, macros are not interactive because the recorded commands do not have variable capabilities. Macros and blocks allow shapes to be defined, stored, and reused. However, neither of these solutions enables user-defined shapes to be modified or manipulated interactively.